1. Field of the Invention
The present invention relates to a separation-material composition for a photo-resist and a manufacturing method of a semiconductor device, and more particularly to a separation-material composition for a photo-resist which is used for separating and removing a remaining photo-resist film, photo-resist residuals and residuals of the by-product polymer after an insulation film is processed with a dry-etching when, for example, a metal wiring is formed on a semiconductor substrate and further to a manufacturing method of a semiconductor device using the separation-material composition for the photo-resist.
The present invention relates especially to a separation-material composition for a photo-resist used when forming a wiring structure of a semiconductor device consisting of a copper wiring and a low dielectric-constant interlayer insulation film, and additionally to a manufacturing method of a semiconductor device using such a separation-material composition for a photo-resist.
2. Description of the Related Art
In recent years, a wiring-working dimension has become minutely smaller and smaller owing to a higher integration of a semiconductor device and at the same time the trend of a multi-layer constitution of the wiring has been progressed. Additionally, there has been a demand for a lower power supply, a high speed operation and the like together with a higher integration.
The increase of a wiring resistance and a wiring capacitance caused by a thinner wiring and a smaller pitch of the wiring leads to a deterioration of the operation speed and an increase of a power consumption. Accordingly, in order to satisfy the demand for a higher integration, for a lower power supply and for a higher operation speed it is necessary and inevitable to use copper which has a low electric resistance as a wiring material and to use a multi-layer wiring where a low dielectric-constant film is made as an interlayer insulation film.
Accordingly, as a material for an insulation film between wirings or for an interlayer insulation film, a silicon oxide film including fluorine, a silicon oxide film including carbon, hydrogen silsequioxane, methyl silsequioxane, polyacryl ether, Teflon (registered trademark) and the like have been investigated instead of a silicon oxide film which is film-made by a chemical vapor deposition (CVD) method or a spin-on coating method widely used at the present time. Hereinafter, insulation films formed by these low dielectric-constant materials are named or designated as low dielectric-constant insulation films (low-k films).
Further, for a wiring material, a Cu wiring which includes copper of a low electric resistance as a main component is investigated to be used instead of an Al wiring which includes aluminum as a main component and which is widely used at the present time. A Cu wiring is difficult to be etching processed as compared with an Al wiring, so that it is worked by a technique of a so-called damascene method.
A damascene method is roughly classified into a single damascene process and a dual damascene process.
A single damascene process is a process which is mainly applied when a wiring of a single layer is formed where a wiring groove of a predetermined pattern is preliminary made on an insulation film and the wiring groove is buried by piling metal layers on the insulation film such that a conductor layer is formed. Subsequently, the metal layers are polished by a certain polishing method such as a CMP method known in the art such that the insulation film will be exposed and at the same time the surface of the insulation film is made flat, and consequently a buried wiring is formed according to this technique.
As shown in FIG. 11A, for example, an insulation film 94 is film-made on a semiconductor substrate 92 on which a device such as a transistor is formed and subsequently an etching-stopper layer 96, a low dielectric-constant insulation film 98 and a cap insulation film 100 are successively film-made. Next, the cap insulation film 100 and the low dielectric-constant insulation film 98 are photolithography processed and etching processed to form a wiring groove 102. Subsequently, a barrier metal film 104/a Cu plated thin film 106 are piled on the cap insulation film 100, and further a Cu layer is piled. Next, the Cu layer and the barrier metal film 104/the Cu plated thin film 106 are polished by a CMP method and the like, so that a Cu-buried wiring 108 is formed in the wiring groove 102.
A dual damascene process is applied when a multi-layer wiring structure composing of a lower layer wiring and an upper layer wiring is formed. A contact hole connecting to the lower layer wiring and a wiring groove connected thereto are dry-etched to form an insulation film layer and the contact hole and the wiring groove are subsequently buried by a metal layer. After the metal film is polished, an electric contact plug which will be connected to a lower layer wiring having a buried contact hole and an upper layer wiring having a buried wiring groove are formed at the same time.
As shown in FIG. 11B, for example, an etching-stopper layer 110, a low dielectric-constant insulation film 112, an etching-stopper layer 114, a low dielectric-constant insulation film 116 and a cap insulation film 118 are successively film-made on the Cu-buried wiring 108 which was made, for example, by the single damascene method.
Next, the cap insulation film 118, the low dielectric-constant insulation film 116, the etching-stopper layer 114, the low dielectric-constant insulation film 112 and the etching-stopper layer 110 are etching processed such that a connecting aperture 119 is opened, and further the cap insulation film 118 and the low dielectric-constant insulation film 116 are etching processed such that a wiring groove 121 is opened.
Subsequently, a barrier metal film 120/a Cu plated thin film 122 are piled on the cap insulation film 118, and further a Cu layer is piled. Next, the Cu layer and the barrier metal film 120/the Cu plated thin film 122 are polished by a CMP method and the like, and a Cu-buried wiring 124 is formed.
It should be noted that in the damascene process, the photo-resist mask is removed by ashing processing the photo-resist mask after the insulation film is etching processed, but photo-resist residuals and its by-product polymer will remain after the ashing process. Unless removing those photo-resist residuals and polymer, there arises a problem that the resistance value between the upper and lower wiring patterns becomes high, the leak current between wirings on the same wiring layer increases and the like.
Consequently, the remaining photo-resist residuals and the by-product polymer are removed by performing a medicinal liquid washing process using a separation liquid composed of an alkaline separation-material or a fluorine compound as its main component.
However, the low dielectric-constant insulation film is easily oxidized or eroded by the alkaline medicinal liquid and additionally it might happen that the hygroscopic characteristic may become higher such that the dielectric constant increases. Consequently, the characteristic of the low dielectric-constant insulation film is deteriorated and there arises a problem that a desired performance of a semiconductor device cannot be obtained.
On the other hand, when a separation-material including fluorine ions is used, the low dielectric-constant film which is oxidized by the etching and ashing processes is eroded and etched by the separation-material including fluorine ions. In this operation a working dimension of the wiring pattern changes, so that there arises a problem that a short-circuit happens between the wirings adjacent each other with respect to up/down or right/left direction.
Further, in the above damascene process, when a stacking structure having a silicon oxide film on the low dielectric-constant insulation film is used as an insulation film, the low dielectric-constant insulation film is selectively eroded and etched, so that the wiring groove has eaves-shaped side walls such that the adherence of the barrier metal layer for the purpose of a diffusion prohibition of the wiring metal becomes insufficient and there is a problem that the wiring metal is diffused in the insulation film.
Additionally, the coverage of the Cu plated thin film becomes inadequate, so that there is a problem that a void where Cu is not piled will be produced.
For example, in the single damascene process, when the washing process is preformed by using a separation-material after forming the wiring groove 102, the low dielectric-constant insulation film 98 is eroded and has a retreat such that the bottom portion of the wiring groove 102 is spread as shown as a circular portion in FIG. 12A.
As a result, the coverage of the barrier metal film 106/the Cu plated thin film 106 becomes inadequate, so that there arises a problem that a void 126 where Cu is not piled in the wiring groove is produced and Cu diffuses to the low dielectric-constant insulation film 98.
Further, the dual damascene process also has similar problems as those of the single damascene process.
In the dual damascene process when the washing process is preformed using a separation-material after forming the contact hole 119 or the wiring groove 121, the low dielectric-constant insulation films 112 and 116 are eroded and have retreats as shown as an arrow A in FIG. 12B.
As a result, the coverage of the barrier metal film 120/the Cu plated thin film 122 becomes inadequate, so that as shown as an arrow B, there arises a problem that a void 128 where Cu is not piled in the wiring groove is produced and Cu diffuses to the low dielectric-constant insulation films 112 and 116.
For both of the single damascene process and the dual damascene process, this problem also becomes the same problem when an insulation film is etching processed by using a hard mask obtained by transferring a pattern of a photo-resist mask to a hard mask forming layer after the hard mask forming layer is film-made and the photo-resist mask is formed on the hard mask forming layer.
Further, when a buried wiring structure buried with Cu in a low dielectric-constant insulation film is formed by such as a dual damascene process and removing a photo-resist mask, portions C of the low dielectric-constant insulation films 112 and 116 which expose from a contact hole 119 and a wiring groove 121 as shown in FIG. 1A change in their quality if a conventionally widely-used amine family medicinal liquid such as a medicinal liquid of EKC 525 which is made by EKC company is used such that the dielectric constant increases.
Further, when a conventional NH4F family medicinal liquid is applied, the low dielectric-constant insulation films 112 and 116 are eroded and have retreats such that eaves shapes are formed by the projections of the etching stopper layer 114 and the cap insulation film 118 as shown in FIG. 1B. Therefore, the coverage of the barrier metal film 120 and the Cu plated thin film 122 becomes inadequate, so that areas are produced where the barrier metal layer 120 and the Cu thin film 122 cannot be piled. As a result, it happens that Cu diffuses to the low dielectric-constant insulation film and a void D of Cu is formed, so that the reliability of wiring is deteriorated and the incidence of sub-standard articles becomes higher.
As an alkaline separation-material has a disadvantage of eroding the low dielectric-constant insulation film as mentioned above, an acid separation-material composed of a calboxylic acid family acid as its main component is also commercially available instead of an alkaline separation-material.
Further, a separation-material composed of phosphonate as its main component is also commercially available for an acid separation-material. Japanese laid-open patent No. 2000-258924, for example, proposes a separation-material composition for a photo-resist containing an oxidant, a phosphonic acid family chelating material and a water-soluble fluorine compound and a separation method of the photo-resist thereof.
Additionally, Japanese laid-open patent No. 2001-345303 proposes a surface processing material using a phosphonate as a complexing agent and an organic alkaline as an organic solvent.
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                Japanese laid-open patent No. 2000-258924 (at page 2)<Document of Patent: 2>        Japanese laid-open patent No. 2001-345303 (at page 3)        
However, the conventional acid separation liquid has a problem for a practical use as explained hereinafter.
In more detail, an acid separation-material composed of a calboxylic acid family acid as its main component and an acid separation-material containing a phosphonic acid family chelating material have low separation abilities of a photo-resist, so that it is difficult to get a satisfactory separation effect in an actual production process.
Additionally, it is necessary to use the acid separation-material containing a phosphonate as a complexing agent in an alkaline area of pH 9 or more, so that there was a problem of a fear that the low dielectric-constant film might change in its quality in the atmosphere of the alkaline area. Further, the concentration of the phosphonate is very low in a range of 1 to 1000 weight ppm, so that the photo-resist separation ability and the polymer removing ability are deemed to be low and it is difficult to get a satisfactory separation effect in an actual production process.
In the above explanation, problems of the separation-material composition for the photo-resist were explained raising the examples of the damascene process, but these are not limited to the damascene process and are also the same problems in general removals of photo-resist masks.